Over the last decade, the rapid improvement of silicon, packaging, integration, battery, wireless, and display technologies has enabled a wide variety of small, portable electronic devices with vastly improved levels of functionality, form factor, and performance. Much of these advances have been driven by the popularity of pocket-sized devices, such as cell phones and MP3 players. These devices now utilize high-resolution color displays, high performance processors, fast and large capacity memories, wireless interconnectivity, and rich user interfaces. However, few of these advanced technologies have crossed over into small wearable devices, such as watches. Because of severe size and battery constraints, wearable electronic devices have had limited functionality and have typically used low power, simplistic electronic displays, such as monochrome LCD or segmented LED. In the past, efforts to incorporate greater performance and functionality into wearable devices have led to large, bulky designs that were awkward to use, expensive, and limited in battery life. To integrate these advanced technologies into wearable form factors, innovation is required, particularly in the area of power management.